The present invention relates to an image pickup apparatus and a method and a system for controlling the exposure of the image pickup apparatus. In particular, it relates to exposure control for use in an image pickup apparatus having an electronic variable shutter.
Recently, electronic variable shutters for electrically changing the exposure period of time of image pickup apparatus have been made available, and video movie cameras with a new exposure control system such as a programmed automatic exposure (AE) system or the like have been marketed. An electronic variable shutter used in a CCD image pickup apparatus is discussed in NIKKEI MICRODEVICE, No. 10, pp 63-64, October 1987. An electronic variable shutter with a programmed AE system used in an MOS image pickup apparatus is discussed in IEEE Transactions on Consumer Electronics, vol. CE-33, No. 3, pp 249-255, August 1987. A technique for shortening the exposure period of time less than a value designated by an operator when detecting an iris value larger than a predetermined value is disclosed in U.S. Pat. No. 4,959,727.